Process for deposition of titanium oxynitride for use in integrated circuit fabrication

ABSTRACT

A process is provided for depositing a substantially amorphous titanium oxynitride thin film that can be used, for example, in integrated circuit fabrication, such as in forming spacers in a pitch multiplication process. The process comprises contacting the substrate with a titanium reactant and removing excess titanium reactant and reaction byproducts, if any. The substrate is then contacted with a second reactant which comprises reactive species generated by plasma, wherein one of the reactive species comprises nitrogen. The second reactant and reaction byproducts, if any, are removed. The contacting and removing steps are repeated until a titanium oxynitride thin film of desired thickness has been formed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/268,260, filed Feb. 5, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/996,062, filed Jun. 1, 2018, now U.S. Pat. No.10,460,928, which is a continuation of U.S. patent application Ser. No.15/384,028, filed Dec. 19, 2016, now U.S. Pat. No. 10,002,755, which isa continuation of U.S. patent application Ser. No. 14/835,465, filedAug. 25, 2015, now U.S. Pat. No. 9,523,148, each of which isincorporated herein by reference in its entirety.

BACKGROUND Field of the Invention

This invention relates generally to the field of semiconductor devicefabrication and, more particularly, to the deposition of titaniumoxynitride (TiO_(x)N_(y)). The titanium oxynitride can be used, forexample, in processes for forming integrated circuits.

Description of Related Art

There is an extremely high demand for integrated circuits to bedecreased in size. This demand stems, for example, from a need forincreased portability, increased computing power, increased memorycapacity, and increased energy efficiency. In order to decrease the sizeof integrated circuits, the sizes of the constituent features,electrical devices and interconnect lines, for example, must be reducedas well.

The demand for reduced size has moved the industry to continuouslyreduce constituent feature size in integrated circuits. For example,memory circuits or devices such as dynamic random access memories(DRAMs), flash memory, static random access memories (SRAMs),ferroelectric (FE) memories are continuously being made smaller.

One example, DRAM typically comprises millions of identical circuitelements, known as memory cells. In its most general form, a memory celltypically consists of two electrical devices: a storage capacitor and anaccess field effect transistor. Each memory cell is an addressablelocation that can store one bit (binary digit) of data. A bit can bewritten to a cell through the transistor and can be read by sensingcharge in the capacitor. By decreasing the sizes of the electricaldevices that constitute, for example, a memory cell and the sizes of theconducting lines that access the memory cells, the memory devices can bemade smaller. Additionally, storage capacities can be increased byfitting more memory cells on a given area in the memory devices.

The continual reduction in feature size places ever greater demands onthe techniques used to form the features. Photolithography, for example,is commonly used to pattern features, such as conductive lines. Whendealing with photolithography, the concept of pitch can be used todescribe the sizes of these features. Pitch is defined as the distancebetween an identical point in two neighboring features. These featuresare typically defined by the spaces between themselves, spaces that aretypically filled by a material, such as an insulator. As a result, pitchcan be viewed as the sum of the width of a feature and of the width ofthe space on one side of the feature separating that feature from aneighboring feature. However, due to factors such as the optics, or thewavelength of light used in the technique, photolithographic techniqueseach have a minimum pitch below which a particular photolithographictechnique cannot reliably form features. Thus, the minimum pitch of aphotolithographic technique is an obstacle to continued feature sizereduction.

Pitch doubling, pitch multiplication, or spacer defined double/quadruplepatterning is a method for extending the capabilities ofphotolithographic techniques beyond their minimum pitch. During a pitchdoubling process a spacer film layer is formed or deposited over anexisting mask feature. The spacer film is then etched, preferably usinga directional etch, such as a reactive ion etch, thereby leaving onlythe spacer, or the material extending or formed from the sidewalls ofthe original mask feature. Upon removal of the original mask feature,only the spacer remains on the substrate. Thus, where a given pitchpreviously included a pattern defining one feature and one space, thesame width now includes two features and two spaces, with the spacesdefined by, in this instance, the spacers. As a result, the smallestfeature size possible with a photolithographic technique is effectivelydecreased. While the pitch is actually halved in the above example, thisreduction in pitch is referred to as pitch “doubling,” because thelinear density of features has been doubled. The process as describedabove can be performed additional times, using the newly formed spacersas the original mask feature to again reduce the pitch by half, orquadruple the linear density of features.

In spacer applications, such as in the pitch multiplication process asdescribed above, materials with specific etch characteristics arerequired for device fabrication. The original maskf feature in a pitchmultiplication process is typically thermal silicon dioxide (SiO₂), withhydrofluoric acid used to etch, or remove, the mask feature. It ispreferable that the thermal SiO₂ mask feature is etched away completelywhile the spacer material remains intact. Therefore, spacer filmmaterials with lower etch rates than that of thermal SiO₂ inhydrofluoric acid are needed.

Additionally, because spacers are formed on the sidewalls ofpre-patterned features, spacer films are preferably conformal. In orderto achieve this conformality, deposition techniques such as atomic layerdeposition (ALD) or plasma enhanced atomic layer deposition (PEALD) aretypically used. The template materials used in pitch multiplicationprocesses, such as SOC materials, can also lower the allowed thermalbudget, thereby favoring lower temperature deposition techniques likePEALD.

Titanium dioxide (TiO₂) is a material which has favorable etchselectivity compared to thermal SiO₂, and can be conformally grown byPEALD at relatively low temperatures. Tetrakis(dimethylamido)titanium(TDMAT) or other alkylamides are typically used as titanium precursors,while O₂ plasma is typically used as an oxygen precursor. TiO₂, however,crystallizes easily, causing roughness in the spacer film which rendersthe resulting spacer unacceptable for its intended use. Although in someconditions smooth, amorphous, TiO₂ could possibly be grown as a thinfilm, it may be difficult up to about 20 nm thick, and above that thegrowth of thicker TiO₂ films leads almost surely to crystallization.

Accordingly, there is a need for methods of forming or depositingconformal thin films that are smooth and amorphous, yet are capable ofbeing deposited to thicknesses greater than is known in the art, whilestill retaining favorable etch selectivity towards SiO₂

SUMMARY OF THE INVENTION

According to one aspect of the present invention, processes are providedfor depositing a titanium oxynitride thin films that can be used, forexample, in integrated circuit fabrication. The process comprisescontacting the substrate with a titanium reactant and removing excesstitanium reactant and reaction byproducts, if any, such as by exposingthe substrate to a purge gas and/or vacuum. The substrate is thencontacted with a second reactant which comprises a plurality of reactivespecies generated by plasma, wherein the plurality of reactive speciescomprises nitrogen and oxygen. The ratio of nitrogen reactive species tooxygen reactive species may be from about 1:2 to about 250:1. Thesubstrate may be exposed to a purge gas and/or vacuum to remove excesssecond reactant and reaction byproducts, if any. The contacting andexposing steps are repeated until a titanium oxynitride thin film ofdesired thickness has been formed. The titanium oxynitride thin film maycomprise from about 0.05 at-% to about 30 at-% of nitrogen.

In some embodiments the processes may be used in integrated circuitfabrication, for example to form spacers. In some embodiments theprocess may be used to form spacers for use in pitch multiplicationprocesses. In some embodiments the titanium oxynitride film may besubstantially amorphous. In some embodiments the substrate may comprisea preexisting mask feature. In some embodiments the titanium reactantmay comprise an alkylamine ligand. In some embodiments the titaniumreactant may comprise Ti(NR^(I)R^(II))₄, wherein R^(I) and R^(II) can beindependently selected to be alkyl groups. In some embodiments thesecond reactant may comprise a nitrogen precursor and an oxygenprecursor. In some embodiments the nitrogen precursor may comprise N₂,NH₃, or N₂H₂. In some embodiments the oxygen precursor may comprise O₂.In some embodiments the reactive species may comprise nitrogen atoms,nitrogen ions, nitrogen radicals, or nitrogen plasma and oxygen atoms,oxygen radicals, or oxygen plasma. In some embodiments deposition may becarried out at a temperature of, preferably from about 70° to about 200°C. In some embodiments the process may be a plasma enhanced atomic layerdeposition process.

According to another aspect of the present invention, processes areprovided for depositing a titanium oxynitride thin film. The processesmay comprise at least one deposition cycle, each cycle comprisingalternately and sequentially contacting the substrate with a titaniumreactant and a second reactant comprising a plurality of reactivespecies, wherein a ratio of nitrogen reactive species to oxygen reactivespecies is from about 1:2 to about 250:1. The titanium oxynitride thinfilm may comprise from about 0.05 at-% to about 30 at-% of nitrogen.

In some embodiments the process may be used to form spacers for use inintegrated circuit fabrication. In some embodiments the titaniumreactant may have the formula Ti(NR^(I)R^(II))₄, wherein R^(I) andR^(II) can be independently selected to be Me or Et. In some embodimentsthe second reactant may comprise a nitrogen precursor and an oxygenprecursor. In some embodiments the reactive species may comprisenitrogen atoms, nitrogen ions, nitrogen radicals, or nitrogen plasma andoxygen atoms, oxygen radicals, or oxygen plasma. In some embodiments theprocess may be a plasma enhanced atomic layer deposition processes.

According to another aspect of the present invention, processes areprovided in which titanium oxide is deposited on a three-dimensionalfeature of a substrate, such as in forming a spacer for use in a pitchmultiplication process. The process may comprise conformally depositinga substantially amorphous titanium oxynitride thin film via PEALD overan existing mask feature in a reaction space. The conformal titaniumoxynitride thin film is preferentially etched from the horizontalsurface of the substrate and mask feature. The mask feature is thenpreferentially etched and the titanium oxynitride deposited on orextending from a vertical surface of the mask feature remains relativelyunetched.

In some embodiments the titanium oxynitride film may be used to formspacers. In some embodiments the spacers may be used in a pitchmultiplication process. In some embodiments preferentially etching thetitanium oxynitride film from horizontal surfaces may comprise areactive ion etch. In some embodiments preferentially etching the maskfeature may comprise a hydrofluoric acid wet etch. In some embodimentsthe substrate may comprise silicon. In some embodiments the mask featuremay comprise SiO₂. In some embodiments conformally depositing asubstantially amorphous titanium oxynitride thin film via PEALD over anexisting mask feature on a substrate in a reaction space may comprisealternately and sequentially contacting the substrate with a titaniumreactant and a second reactant comprising a plurality of reactivespecies. In some embodiments the second reactive species has a ratio ofnitrogen reactive species to oxygen reactive species that may be fromabout 1:2 to about 250:1. In some embodiments the titanium oxynitridethin film may comprise from about 0.05 at-% to about 30 at-% ofnitrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating a process for depositing a titaniumoxynitride thin film by a plasma enhanced ALD process according to someembodiments of the present disclosure.

FIG. 2A illustrates a cross-sectional view of a step of an exemplaryspacer deposition process according to some embodiments.

FIG. 2B illustrates a cross-sectional view of a step of an exemplaryspacer deposition process according to some embodiments.

FIG. 2C illustrates a cross-sectional view of a step of an exemplaryspacer deposition process according to some embodiments.

FIG. 2D illustrates a cross-sectional view of a step of an exemplaryspacer deposition process according to some embodiments.

FIG. 3A is a scanning electron micrograph of a reference titanium oxidethin film.

FIG. 3B is a scanning electron micrograph of an exemplary TiO_(x)N_(y)film deposited by a deposition process according to some embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Crystallization in TiO₂ thin films can be suppressed by adding foreignatoms to the material. In preferred embodiments of the presentinvention, nitrogen atoms are present in the plasma during plasmaenhanced atomic layer deposition (PEALD), thereby depositing nitrogendoped TiO₂, or titanium oxynitride (TiO_(x)N_(y)). The resultantTiO_(x)N_(y) deposited by PEALD will be less crystalline than pure TiO₂grown at the same deposition conditions.

In some common integrated circuit fabrication processes, for example,pitch multiplication processes, the spacers and original mask featureare simultaneously exposed to an etchant, typically hydrofluoric acid,which preferentially etches the original mask feature. As titaniumdioxide has etch selectivity towards silicon based materials such assilicon dioxide, an SiO₂ mask feature can be preferentially etched whilea TiO₂ spacers that have been conformally deposited on the side walls ofthe mask feature can remain relatively unetched. Therefore, etchselectivity relative to SiO₂ is an important characteristic of anymaterial comprising a spacer. Although foreign atoms can be introducedinto the spacer material, it is important that these foreign atoms notsignificantly impair the etch selectivity of the spacer material.Additionally, titanium oxynitride films deposited according to theprocesses described herein may be useful as a sacrificial film in, forexample, patterning applications.

Additionally, titanium is an oxyphilic element, meaning that titaniumpreferentially combines with oxygen atoms. Therefore, large nitrogen tooxygen ratios are needed in the plasma during the PEALD process in orderto deposit TiO_(x)N_(y) with a sufficient amount of nitrogenincorporated into the material to achieve a smooth, amorphous film.

In view of these difficulties, preferred embodiments disclosed hereinallow for conformal deposition of substantially amorphous TiO_(x)N_(y)thin films that are less crystalline than pure TiO₂, but still retainetch selectivity relative to SiO₂. These films can be used, for example,as sacrificial films in patterning application and as spacers inintegrated circuit formation, such as in a pitch multiplication process.

PEALD Processes

In some embodiments, plasma enhanced ALD (PEALD) processes are used todeposit TiO_(x)N_(y) films. Briefly, a substrate or workpiece issubjected to alternately repeated surface reactions. In someembodiments, thin TiO_(x)N_(y) films are formed by repetition of an ALDcycle. Preferably, for forming TiO_(x)N_(y) films, each ALD cyclecomprises at least two distinct phases. The contacting and removal of areactant from the substrate surface may be considered a phase. In afirst phase, a first reactant comprising titanium contacts the substratesurface and conformally forms no more than about one monolayer on thesubstrate. This reactant is also referred to herein as “the titaniumprecursor,” “titanium-containing precursor,” or “titanium reactant” andmay be, for example, alkylamine titanium compound, such as TDMAT. In asecond phase, a second reactant comprising a reactive species ormultiple reactive species contacts the substrate surface and may convertadsorbed titanium to TiO_(x)N_(y). In some embodiments the secondreactant comprises an oxygen precursor and a nitrogen precursor. In someembodiments, the reactive species comprises one or more excited species.In some embodiments the second reactant comprises one or more speciesfrom a nitrogen and oxygen containing plasma. In some embodiments, thesecond reactant comprises nitrogen radicals, nitrogen atoms, and/ornitrogen plasma and oxygen radicals, oxygen atoms, and/or oxygen plasma.The second reactant may comprise other species that are not nitrogen oroxygen precursors. In some embodiments, the second reactant may comprisea plasma of hydrogen, radicals of hydrogen, or atomic hydrogen in oneform or another. In some embodiments, the second reactant may comprise aspecies from a noble gas, such as He, Ne, Ar, Kr, or Xe, preferably Aror He, for example as radicals, in plasma form, or in elemental form.These reactive species from noble gases do not necessarily contributematerial to the deposited film, but can in some circumstances contributeto film growth as well as help in the formation and ignition of plasma.In some embodiments the second reactant may comprise a gas that acts asa carrier gas for the second reactant. In some embodiments a carrier gasthat is used to form a plasma may flow constantly throughout thedeposition process but only be activated intermittently. Additionalphases may be added and phases may be removed as desired to adjust thecomposition of the final film.

One or more of the reactants may be provided with the aid of a carriergas, such as Ar or He. In some embodiments the titanium precursor andthe second reactant are provided with the aid of a carrier gas. In someembodiments, two of the phases may overlap, or be combined. For example,the titanium precursor and the second reactant may be providedsimultaneously in pulses that partially or completely overlap. Inaddition, although referred to as the first and second phases, and thefirst and second reactants, the order of the phases may be varied, andan ALD cycle may begin with any one of the phases. That is, unlessspecified otherwise, the reactants can be provided in any order, and theprocess may begin with any of the reactants.

In some embodiments the substrate is contacted with a first reactant andthe substrate is moved such that it is contacted with a second reactant.In some embodiments the substrate can be moved within a single reactionspace. In some embodiments the substrate can be moved from a firstreaction space to a second, different reaction space.

The substrate can comprise various types of materials. The substrate maybe, for example, a semiconductor substrate. In some embodiments thesubstrate may comprise silicon. In some embodiments the substrate maycomprise at least one of silicon dioxide and silicon nitride.

As discussed in more detail below, in some embodiments for depositing aTiO_(x)N_(y) film, one or more deposition cycles begin with contactingthe substrate surface with the titanium precursor, followed by thesecond reactant. In other embodiments deposition may begin withcontacting the surface with the second reactant, followed by thetitanium precursor.

In some embodiments, if necessary, the exposed surfaces of the substrateor workpiece can be pretreated to provide reactive sites to react withthe first phase of the ALD process. In some embodiments a separatepretreatment step is not required. In some embodiments the substrate ispretreated to provide a desired surface termination. In some embodimentsthe substrate is pretreated with plasma.

Excess reactant and reaction byproducts, if any, are typically removedfrom the vicinity of the substrate, and in particular from the substratesurface, between reactant pulses. In some embodiments the reactionchamber is purged between reactant pulses, such as by purging with aninert gas. The flow rate and time of each reactant, is tunable, as isthe removal step, allowing for control of the quality and variousproperties of the films. In some other embodiments the reaction chamberis purged by stopping the flow of a precursor or reactant and continuingto flow carrier gas into the chamber. In some embodiments excessreactant and reaction byproducts are removed from the vicinity of thesubstrate by moving the substrate. In some embodiments the substrate ismoved within a reaction chamber. In some embodiments the substrate ismoved from a first reaction chamber to a second, different reactionchamber.

As mentioned above, in some embodiments a carrier gas is provided to thereaction chamber continuously during each deposition cycle, or duringthe entire ALD process, and reactive species are provided. Reactivespecies may be provided by generating a plasma in the gas, either in thereaction chamber or upstream of the reaction chamber, and may also beprovided by injection into the carrier gas. In some embodiments thecarrier gas may comprise helium, or argon. In some embodiments thecarrier gas may also serve as a purge gas for the first and/or secondreactant (or reactive species). In some embodiments the purge gas may bea reactant, for example, flowing the second reactant may serve as apurge gas for a first titanium precursor and also serve as reactivespecies when a plasma is formed in the gas. In some embodiments,nitrogen, argon, or helium may serve as a purge gas for a firstprecursor and a source of excited species for converting the titaniumprecursor into the TiO_(x)N_(y) film.

The ALD cycle is repeated until a film of the desired thickness andcomposition is obtained. In some embodiments the deposition parameters,such as the flow rate, flow time, contact time, purge time, removaltime, RF Power, RF on time and/or precursors themselves, may be variedin one or more deposition cycles during the ALD process in order toobtain a film with the desired characteristics.

The term “pulse” may be understood to comprise feeding reactant into thereaction chamber for a predetermined amount of time. The term “pulse”does not restrict the length or duration of the pulse and a pulse can beany length of time.

In some embodiments, the titanium precursor contacts the substratefirst. After an initial surface termination, if necessary or desired,the substrate is contacted with a titanium precursor. In accordance withsome embodiments, the titanium precursor contacts the substrate via afirst titanium precursor pulse comprising a carrier gas flow and avolatile titanium species, such as TDMAT, that is reactive with thesubstrate surfaces of interest. Accordingly, the titanium precursoradsorbs upon these substrate surfaces. The first precursorself-saturates the substrate surfaces such that any excess constituentsof the first precursor pulse do not further react with the molecularlayer formed by this process.

The titanium precursor preferably contacts the substrate in gaseousform. The titanium precursor gas is considered “volatile” for purposesof the present description if the species exhibits sufficient vaporpressure under the process conditions to transport the species to thesubstrate in sufficient concentration to saturate exposed surfaces. Insome embodiments the titanium precursor contacts the substrate byinjecting the titanium precursor into the carrier gas. In some otherembodiments the titanium precursor contacts the substrate separatelyfrom any carrier gas or inert gas flow.

In some embodiments the titanium precursor contact duration is fromabout 0.05 to about 10.0 seconds, preferably from about 0.1 to about 5seconds and more preferably from about 0.1 to about 1.0 seconds.Conditions are preferably selected such that no more than about onemonolayer of the titanium precursor is adsorbed on the substrate surfacein a self-limiting manner. In some embodiments the appropriate titaniumprecursor contact duration can be longer or shorter depending on theparticular circumstances. The appropriate contact duration can bereadily determined by the skilled artisan based on the particularcircumstances.

After sufficient time for a molecular layer to adsorb on the substratesurface, excess titanium precursor is then removed from the substratesurface. In some embodiments the excess titanium precursor is removed bystopping the flow of the titanium precursor while continuing to flow acarrier gas or purge gas for a sufficient time to diffuse or purgeexcess reactants and reactant by-products, if any, from the reactionspace. In some embodiments the excess titanium precursor is removed withthe aid of an inert gas that is flowing throughout the ALD cycle. Insome embodiments the titanium precursor is removed by stopping the flowof the titanium precursor and starting to flow a carrier gas or purgegas. In some embodiments the titanium precursor is removed from thesubstrate surface by moving the substrate within a reaction chamber. Insome embodiments the titanium precursor is removed from the substratesurface by moving the substrate from a first reaction chamber to asecond, different reaction chamber.

In some embodiments the titanium precursor contact duration is fromabout 0.05 to about 10.0 seconds, preferably from about 0.1 to about 5seconds and more preferably from about 0.1 to about 2.0 seconds. In someembodiments the appropriate titanium precursor removal duration can belonger or shorter, depending on the particular circumstances. Theappropriate removal duration can be readily determined by the skilledartisan based on the particular circumstances. The typical precursorpurge duration is also about 0.1 to about 1.0 seconds. This is alsodepends on each condition.

In the second phase, a plurality of reactive species, such as a plasmacomprising oxygen and nitrogen reactive species contact the surface ofthe substrate. A carrier gas may be flowed continuously to the reactionchamber during each ALD cycle in some embodiments. A plasma may beformed by generating a plasma in the second reactant in the reactionchamber or upstream of the reaction chamber, for example by flowing thesecond reactant through a remote plasma generator. In some embodiments,plasma is generated in the flowing second reactant. In some embodimentsthe second reactant contacts the surface of the substrate before theplasma is ignited or nitrogen and oxygen atoms or radicals are formed.In some embodiments the second reactant is introduced into the reactionchamber by injecting the second reactant into a carrier gas. In someother embodiments the second reactant contacts the surface of thesubstrate separately from any carrier gas or inert gas.

In some embodiments the titanium precursor contact duration is fromabout 0.05 to about 10.0 seconds, preferably from about 0.1 to about 5seconds and more preferably from about 0.1 to about 2.0 seconds. In someembodiments the appropriate second reaction contact duration can belonger or shorter depending on the particular circumstances. Theappropriate contact duration can be readily determined by the skilledartisan based on the particular circumstances.

In some embodiments the substrate may be contacted with the secondreactant while the titanium precursor is still present at the substratesurface. In some embodiments the second reactant may contact thesubstrate prior to the removal of the titanium precursor from thesurface of the substrate. In some embodiments the substrate may becontacted with the titanium precursor while the second reactant is stillpresent at the substrate surface. In some embodiments the titaniumprecursor may contact the substrate prior to the removal of the secondreactant from the surface of the substrate.

After a time period sufficient to completely saturate and react thepreviously adsorbed molecular layer with the plasma pulse, any excessreactant and reaction byproducts are removed from the substrate surface.As with the removal of the first reactant/precursor, in some embodimentsthis step may comprise stopping the generation of reactive species inthe second reactant and continuing to flow the carrier gas for a timeperiod sufficient for excess reactive species and volatile reactionby-products to diffuse out of and be purged from the reaction space. Insome other embodiments removal may comprise stopping generating reactivespecies in the second reactant, stopping the flow of the secondreactant, and continuing to flow the carrier gas. In other embodimentsthe generation of reactive species in the second reactant is stopped anda separate purge gas may be used. In some embodiments the generation ofreactive species in the second reactant is stopped, the flow of secondreactant into the reaction chamber is stopped, and separate purge gasmay be used. In some embodiments the substrate is moved such that thesecond reactant/precursor no longer contacts the substrate. In someembodiments the substrate is moved within a reaction chamber. In someembodiments the substrate is moved from a first reaction chamber to asecond, different reaction chamber. Together, the second reactant plasmaprovision and removal represent a second phase in a titanium oxynitrideatomic layer deposition cycle.

In some embodiments the titanium precursor contact duration is fromabout 0.05 to about 10.0 seconds, preferably from about 0.1 to about 5seconds and more preferably from about 0.1 to about 2.0 seconds. In someembodiments the appropriate second precursor removal duration can belonger or shorter, depending on the particular circumstances. Theappropriate removal duration can be readily determined by the skilledartisan based on the particular circumstances. A plasma may be generatedby applying RF power to the second reactant. The RF power may be appliedto second reactant that flows during the second reactant plasma pulsetime, that flows continuously through the reaction chamber, and/or thatflows through a remote plasma generator. Thus in some embodiments theplasma is generated in situ, while in other embodiments the plasma isgenerated remotely. In some embodiments the RF power applied to thesecond reactant is from about 10 W to about 2000 W, preferably fromabout 100 W to about 1000 W and more preferably from about 200 W toabout 500 W. In some embodiments RF power may be more than 2000 W if itis desired and for example, if the substrate tolerates it withoutdamage.

The two phases together represent one ALD cycle, which is repeated toform TiO_(x)N_(y) thin films of a desired thickness. While the ALD cycleis generally referred to herein as beginning with the titanium precursorphase, it is contemplated that in other embodiments the cycle may beginwith the second reactant phase. One of skill in the art will recognizethat the first precursor phase generally reacts with the terminationleft by the last phase in the previous cycle. Thus, while no reactantmay be previously adsorbed on the substrate surface or present in thereaction space if the reactive species phase is the first phase in thefirst ALD cycle, in subsequent cycles the reactive species phase willeffectively follow the titanium phase.

Additional phases may be added and phases may be removed as desired toadjust the composition of the final film. In some embodiments, two ofthe phases may overlap, or be combined. For example, the titaniumprecursor and the second reactant may be provided simultaneously inpulses that partially or completely overlap. In addition, althoughreferred to as the first and second phases, and the first and secondreactants, the order of the phases may be varied, and an ALD cycle maybegin with any one of the phases. That is, unless specified otherwise,the reactants can be provided in any order, and the process may beginwith any of the reactants.

According to some embodiments of the present disclosure, PEALD reactionsmay be performed at temperatures ranging from about 20° C. to about 500°C., preferably from about 20° C. to about 450° C., more preferably fromabout 50° C. to about 300° C. and most preferably from about 70° C. toabout 200° C. In some embodiments the PEALD reactions may be performedat pressures ranging from about 10 Pa to about 2000 Pa, preferably fromabout 100 Pa to about 1000 Pa, more preferably from about 200 Pa toabout 400 Pa.

FIG. 1 is a flow chart generally illustrating a titanium oxynitrideplasma enhanced ALD deposition cycle that can be used to deposit atitanium oxynitride thin film in accordance with some embodiments on theinvention. According to certain embodiments, a titanium oxynitride thinfilm is formed on a substrate by an ALD-type process comprising multipletitanium oxynitride deposition cycles, each titanium oxynitridedeposition cycle 100 comprising:

(1) contacting a substrate with a titanium reactant 110 such that thetitanium compound adsorbs on the substrate surface;

(2) removing excess titanium precursor and any byproducts from thesubstrate surface 120;

(3) contacting the substrate with a second reactant 130 comprising aplurality of reactive species generated by plasma, the plurality ofreactive species comprising nitrogen and oxygen; and

(4) removing excess second reactant and reaction byproducts from thesubstrate surface 140.

The contacting and removing steps are repeated 150 until a thin film ofa desired thickness and composition is obtained.

According to some embodiments a titanium oxynitride plasma enhanced ALDdeposition cycle can be used to deposit a titanium oxynitride thin film.In certain embodiments, a titanium oxynitride thin film is formed on asubstrate by an ALD-type process comprising multiple titanium oxynitridedeposition cycles, each titanium oxynitride deposition cycle comprising:

(1) contacting a substrate with a titanium reactant such that thetitanium compound adsorbs on the substrate surface;

(2) exposing the substrate to a purge gas and/or vacuum;

(3) contacting the substrate with a second reactant comprising aplurality of reactive species generated by plasma, the plurality ofreactive species comprising nitrogen and oxygen; and

(4) exposing the substrate to a purge gas and/or vacuum.

The contacting and removing steps are repeated until a thin film of adesired thickness and composition is obtained.

In some embodiments the exposing the substrate to a purge gas and/orvacuum steps may comprise continuing the flow of an inert carrier gaswhile stopping the flow of a precursor or reactant. In some embodimentsthe exposing the substrate to a purge gas and/or vacuum steps maycomprise stopping the flow of a precursor and a carrier gas into areaction chamber and evacuating the reaction chamber, for example with avacuum pump. In some embodiments the exposing the substrate to a purgegas and/or vacuum steps may comprise moving the substrate from a firstreaction chamber to a second, different reaction chamber containing apurge gas. In some embodiments the exposing the substrate to a purge gasand/or vacuum steps may comprise moving the substrate from a firstreaction chamber to a second, different reaction chamber under a vacuum.

In certain embodiments, a titanium oxynitride thin film is formed on asubstrate by an ALD-type process comprising multiple titanium oxynitridedeposition cycles, each titanium oxynitride deposition cycle comprising:alternately and sequentially contacting the substrate with a firsttitanium reactant and a second reactant comprising reactive species. Insome embodiments the second reactive species may comprise

Ti Precursors

A number of suitable titanium precursors can be used in the presentlydisclosed PEALD processes for forming TiO_(x)N_(y). In some embodimentsthe titanium precursor comprises an organometallic precursor. In someembodiments the titanium precursor is tetravalent (that is, Ti has anoxidation state of +IV). In some embodiments the titanium precursorcomprises at least one alkylamide ligand. In some embodiments thetitanium precursor comprises at least one halide ligand. In someembodiments the titanium precursor does not comprise a halide ligand. Insome embodiments the titanium precursor does not comprise four halideligands. In some embodiments the titanium precursor may comprise atleast one amine or alkylamine ligand, —NR^(I)R^(II), wherein R^(I) andR^(II) can be independently chosen from alkyl ligands, preferably ethylor methyl. In some embodiments the titanium precursor may comprise atleast one alkoxide ligand. In some embodiments the titanium precursormay comprise a heteroleptic compound. In some embodiments the titaniumprecursor comprises tetrakis(dialkylamino)titanium compoundsTi(NR^(I)R^(II))₄, such as tetrakis(dimethylamino)titanium (TDMAT)Ti(NMe₂)₄.

In some embodiments the titanium precursor comprises a halide ligand. Insome embodiments the titanium precursor comprises at least one of TiCl₄,TiF₄, TiI₄, TiBr₄. In some instances halide ligands at certain processparameter, such as at high temperature ranges may promotecrystallization of TiO₂ crystals and promote roughness and/or reducesmoothness in a thin film. However, in certain embodiments halideligands may be used while still providing reduced crystallization androughness as compared to pure TiO₂ films of a similar thickness.

In some embodiments the titanium precursor comprises at least one alkylor substituted alkyl ligand. In some embodiments the titanium precursorcomprises an alkoxide. In some embodiments the titanium precursorcomprises at least one of titanium methoxide Ti(OMe)₄, titanium ethoxideTi(OEt)₄, and titanium isopropoxide (Ti(O^(i)Pr)₄ or TTiP).

In some embodiments the titanium precursor comprises at least one amineor alkylamine ligand. In some embodiments the titanium precursorcomprises at least one of Ti(NMeEt)₄ (TEMAT), Ti(N(Et)₂)₄ (TDEAT), andTi(N(Me)₂)₄ (TDMAT).

In some embodiments the titanium precursor comprises a heterolepticprecursor. In some embodiments the titanium precursor comprises at leastone of Ti(O^(i)Pr)₂(dmae)₂, Ti(Me₅Cp)(OMe)₃, Ti(MeCp)(OMe)₃,TiCp(NMe₂)₃, Ti(Me₅Cp)(NMe₂)₃, Ti(mpd)(thd)₂, and Ti(O^(i)Pr)₂(thd)₂. Insome embodiments the titanium precursor comprises a cyclic ligand, suchas a cyclopentadienyl or a derivative of a cyclopentadienyl ligand. Insome embodiments the titanium precursor has at least one Ti—N bond. Insome embodiments the titanium precursor has at least one —Ti—N—C— bondstructure.

In some embodiments more than one titanium precursor may contact thesubstrate surface at the same time during an ALD phase. In someembodiments the titanium precursor may comprises more than one titaniumreactant. In some embodiments a first titanium precursor is used in afirst ALD cycle and a second, different titanium precursor is used in alater ALD cycle. In some embodiments multiple titanium precursors may beused during a single ALD phase, for example, in order to optimizecertain properties of the deposited TiO_(x)N_(y) film.

Second Reactant

As discussed above, the second reactant in a PEALD process used to formTiO_(x)N_(y) according to the present disclosure may comprise a nitrogenprecursor and an oxygen precursor, which may comprise plasma generatedfrom oxygen and nitrogen precursors. Suitable plasma compositionsinclude nitrogen plasma, radicals of nitrogen, or atomic nitrogen, andoxygen plasma, radicals of oxygen, or atomic oxygen in one form oranother. In some embodiments a plasma may also contain hydrogen, such ashydrogen plasma, radicals of hydrogen, or atomic hydrogen in one form oranother. And in some embodiments, a plasma may also contain noble gases,such as He, Ne, Ar, Kr and Xe, preferably Ar or He, in plasma form, asradicals, or in atomic form. In some embodiments, the second reactantdoes not comprise any species from a noble gas, such as Ar. Thus, insome embodiments plasma is not generated in a gas comprising a noblegas.

In some embodiments the second reactant may comprise plasma formed fromboth compounds having N and compounds having O, such as a mixture of N₂and O₂, or a mixture of NH₃ and O₂. In some embodiments the secondreactant may comprise plasma from compounds having O and may notcomprise compounds having N. In some embodiments the second reactant maybe formed at least in part, from an N-containing compound and anO-containing compound, where the N-containing compound and O-containingcompound are provided at a ratio (N-containing compound/O-containingcompound) from about 1:1 to about 100:1, preferably from about 10:1 toabout 30:1. In some embodiments the ratio is from about 1:2 to about250:1. In some embodiments the ratio is about 19:1. In some embodimentsthe second reactant may be formed at least in part, from N₂ and O₂,where the N₂ and O₂ are provided at a ratio (N₂/O₂) from about 1:1 toabout 100:1, preferably from about 10:1 to about 30:1. In someembodiments the second reactant may be formed at least in part, from NH₃and O₂, where the NH₃ and O₂ are provided at a ratio (NH₃/O₂) from about1:1 to about 100:1, preferably from about 10:1 to about 30:1.

In some embodiments wherein the deposited film comprises carbon thesecond reactant may be formed at least in part, from an N-containingcompound and an O-containing compound, where the N-containing compoundand O-containing compound are provided at a ratio (N-containingcompound/O-containing compound) from about 1:1 to about 100:1,preferably from about 10:1 to about 30:1 and more preferably about 19:1.In some embodiments ratio is from about 1:2 to about 250:1. In someembodiments the second reactant may comprise plasma formed from bothcompounds having N and compounds having O, such as a mixture of N₂ andO₂. In some embodiments the second reactant may be formed at least inpart, from N₂ and O₂, where the N₂ and O₂ are provided at a ratio(N₂/O₂) from about 1:1 to about 100:1, preferably about 19:1.

In some embodiments the second reactant may comprise plasma formed fromboth compounds having N and compounds having O. In some embodiments thesecond reactant may not comprise plasma formed from compounds having N.Where the second reactant comprises a compound having N, the compoundshaving N may be selected from at least one of N₂, NH₃, N₂H₄ and N₂H₂.The compounds having O may be selected from at least one of O₃, N₂O,CO₂, CO, H₂O, and H₂O₂. It is to be noted that the ratio reactivespecies, like of N and O species, may be different before plasmaignition (i.e. gas flow ratios) and after plasma ignition (reactivespecies ratio).

The second reactant may be formed in some embodiments remotely viaplasma discharge (“remote plasma”) away from the substrate or reactionspace. In some embodiments, the second reactant may be formed in thevicinity of the substrate or directly above substrate (“direct plasma”).

In some embodiments the second reactant may be provided into a reactionchamber. In some embodiments a suitable second reactant can includecompounds having N, compounds having O, and an inert carrier gas.Various reactant flow rates can be suitable. In some embodiments thesecond reactant may comprise N2, O2, and Ar. In some embodiments a flowrate for N2 is from about 0 slm to about 10 slm. In some embodiments aflow rate for O2 is from about 0.001 slm to about 10 slm. In someembodiments a flow rate for Ar is from about 0 slm to about 10 slm.

TiO_(x)N_(y) Film Characteristics

TiO_(x)N_(y) thin films deposited according to some of the embodimentsdiscussed herein may comprise nitrogen. In some embodiments the ratio ofnitrogen to oxygen in the second reactant when depositing a TiO_(x)N_(y)thin film is from about 1:1 to about 100:1, preferably from about 10:1to about 30:1 and more preferably about 19:1. In some embodiments theratio of oxygen to nitrogen in a TiO_(x)N_(y) thin film is from about1:2 to about 1000:1, preferably from about 1:1 to about 500:1 and morepreferably about 10:1 to about 500:1. In some embodiments the amount ofnitrogen in the deposited TiO_(x)N_(y) thin film is from about 0.05 at-%to about 30 at-%, more preferably from about 0.1 at-% to about 10 at-%and most preferably from about 0.2 at-% to about 5 at-%. In someinstances the amount of nitrogen is less than about 1 at-%. In someinstances the amount of nitrogen is more than about 0.2 at-%. In someinstances the amount of nitrogen is more than about 1 at-%.

In some embodiments the deposited TiO_(x)N_(y) thin film does notcomprise an appreciable amount of carbon. However, in some embodiments aTiO_(x)N_(y) film comprising carbon is deposited. For example, in someembodiments an ALD reaction is carried out using a titanium precursorcomprising carbon and a thin TiO_(x)N_(y) film comprising carbon isdeposited. In some embodiments the amount of O containing compound inthe second reactant can be decreased in order to increase the amount ofcarbon present in the deposited TiO_(x)N_(y) thin film. In someembodiments the amount of carbon in the deposited TiO_(x)N_(y) thin filmis from about 0.05 at-% to about 30 at-%, more preferably from about 0.1at-% to about 10 at-% and most preferably from about 0.1 at-% to about 5at-%. In some instances the amount of carbon is less than about 1 at-%.

In some embodiments, TiO_(x)N_(y) films are deposited to a thicknessesof from about 1 nm to about 50 nm, preferably from about 3 nm to about30 nm, more preferably from about 5 nm to about 20 nm. These thicknessescan be achieved in feature sizes (width) below about 100 nm, preferablyabout 50 nm, more preferably below about 30 nm, most preferably belowabout 20 nm, and in some cases below about 15 nm. According to someembodiments, a TiO_(x)N_(y) film is deposited on a three-dimensionalstructure and the thickness at a sidewall may be slightly even more than10 nm.

In some embodiments amorphous TiO_(x)N_(y) films of greater than 50 nmcan be grown. In some embodiments TiO_(x)N_(y) films of greater than 100nm can be grown. In some embodiments, the film is from about 1 nm toabout 200 nm thick, preferably from about 2 nm to about 100 nm thick. Insome embodiments the film is from about 1 nm to about 20 nm thick. Insome embodiments the film is from about 1 nm to about 10 nm thick.

According to some embodiments TiO_(x)N_(y) films with various wet etchrates (WER) may be deposited. In some embodiments the WER is from about0.01 nm/min to about 200 nm/min, preferably from about 0.01 nm/min toabout 50 nm/min. When using a blanket WER in 1% dHF (nm/min), depositedTiO_(x)N_(y) films may have WER values substantially similar to those ofpure titanium oxide. In some embodiments the deposited TiO_(x)N_(y) thinfilm may have a WER of about 5.2 nm/min.

In some embodiments TiO_(x)N_(y) films with various dry etch rates (DER)may be deposited. In some embodiments a TiO_(x)N_(y) film may have a DERfor a common chlorine based etchant gas, such as BCl₃ gas, that is about5 to about 15 times larger than a DER of Tox (thermal oxide). In someembodiments a TiO_(x)N_(y) thin film may have a DER for a commonfluorine based gas, such CF₄ gas, that is less than about half of a DERof Tox. In some embodiments, the DER of a TiO_(x)N_(y) thin film is lessthan the etch rate of thermal oxide, preferably less than about 0.5times the thermal oxide etch rate, while in other embodiments the DER ofa TiO_(x)N_(y) thin film is more than about 5 larger than a thermaloxide etch rate.

According to some embodiments, the TiO_(x)N_(y) thin films may exhibitstep coverage and pattern loading effects of greater than about 50%,preferably greater than about 80%, more preferably greater than about90%, and most preferably greater than about 95%. In some cases stepcoverage and pattern loading effects can be greater than about 98% andin some case about 100% (within the accuracy of the measurement tool ormethod). These values can be achieved in aspect ratios of more thanabout 2 and aspect ratios more than about 3, preferably in aspect ratiosmore than 5, more preferably in aspect ratios more than 10 and mostpreferably in aspect ratios more than 15. In some embodiments depositedTiO_(x)N_(y) thin films may exhibit substantially the same conformalityas titanium oxide films of the same thickness.

As used herein, “pattern loading effect” is used in accordance with itsordinary meaning in this field. While pattern loading effects may beseen with respect to impurity content, density, electrical propertiesand etch rate, unless indicated otherwise the term pattern loadingeffect when used herein refers to the variation in film thickness in anarea of the substrate where structures are present. Thus, the patternloading effect can be given as the film thickness in the sidewall orbottom of a feature inside a three-dimensional structure relative to thefilm thickness on the sidewall or bottom of the three-dimensionalstructure/feature facing the open field. As used herein, a 100% patternloading effect (or a ratio of 1) would represent about a completelyuniform film property throughout the substrate regardless of featuresi.e. in other words there is no pattern loading effect (variance in aparticular film property, such as thickness, in features vs. open fieldand/or vs. feature dimensions and spacings).

In some embodiments a deposited TiO_(x)N_(y) thin film may have aroughness (RMS) of less than about 0.5 nm, preferably less than about0.3 nm, more preferably less than about 0.2 nm and most preferably lessor equal to about 0.15 nm. In some embodiments a deposited TiO_(x)N_(y)thin film is less crystalline than a pure TiO₂ thin film of the samethickness and deposited with the same precursors.

Integrated Circuit Fabrication Processes

The PEALD process described herein can be used to form TiO_(x)N_(y)films for use, for example, in integrated circuit fabrication. ATiO_(x)N_(y) film may be used as, for example, a sacrificial film inpatterning application, or may be used as spacers for use in pitchmultiplication processes. By way of example, in a pitch multiplicationprocess, TiO_(x)N_(y) is conformally deposited via plasma enhanced ALDin a reaction space on a substrate comprising an existing mask feature.The conformal, smooth, and substantially amorphous TiO_(x)N_(y) film canthen be directionally etched so that TiO_(x)N_(y) is removed from thehorizontal surfaces of the mask feature and substrate, leaving only theTiO_(x)N_(y) deposited on or extending from the sidewalls of the maskfeature. The mask feature can then be removed via an etching process,leaving behind the pitch doubled TiO_(x)N_(y) features.

In preferred embodiments of the invention the ratio of nitrogenprecursor to oxygen precursor comprising the second reactant in thePEALD process is such that the resultant titanium oxynitride thin filmis substantially amorphous when or if grown thicker than 50 nm. As aconsequence of remaining substantially amorphous, the resultantTiO_(x)N_(y) thin film is smooth enough for use as a in a variety ofcontexts, for example as a spacer or sacrificial film. In preferredembodiments of the invention a TiO_(x)N_(y) thin film is grown via PEALDthat is substantially free of crystallites. In some embodiments theratio of nitrogen precursor to oxygen precursor is such that theresultant TiO_(x)N_(y) thin film is substantially less crystalline thana pure TiO₂ thin film grown at the same deposition conditions. In someembodiments of the invention the titanium oxynitride thin film has etchselectivity towards SiO₂, that is an etchant will preferentially etchSiO₂ as compared to the TiO_(x)N_(y) film. In preferred embodiments ofthe invention, the TiO_(x)N_(y) film has a substantially similar etchselectivity towards SiO₂ to pure TiO₂.

With reference to FIG. 2A, and in some embodiments of the presentinvention the substrate comprises a thermal SiO₂ layer 210 on a siliconsubstrate 200. In some embodiments the substrate comprises a siliconbased layer, such as a Si, SiO₂ or SiN_(x) layer on a silicon substrate.In some embodiments the substrate comprises a sacrificial layer. In someembodiments the substrate comprises a polymer or photoresist film. Inpreferred embodiments of the invention the substrate comprises at leastone mask feature 220, such as a three-dimensional raised feature. Inpreferred embodiments the mask feature comprises an elevated structurethat includes substantially vertical sidewalls 221. In some embodimentsof the invention the mask feature is photolithographically formed bytransferring a pattern formed in a photoresist layer to a SiO₂ layer ona silicon substrate.

As shown in FIG. 2B, and in preferred embodiments of the invention theTiO_(x)N_(y) film 230 is conformally deposited over the mask feature220, or features, and substrate 200. After a smooth, substantiallyamorphous TiO_(x)N_(y) thin film has been conformally deposited over amask feature on a substrate, the TiO_(x)N_(y) thin film is directionallyetched. As shown in FIG. 2C and in some embodiments the directional etchpreferentially etches the TiO_(x)N_(y) thin film from the horizontalsurfaces 222, 211 of the mask feature 220 and substrate 200 whileleaving the TiO_(x)N_(y) 231 deposited on the vertical surfaces orsidewalls 221 of the mask feature 220 relatively unetched. In preferredembodiments the directional etch is a reactive ion etch. In preferredembodiments the directional etching removes substantially all of theTiO_(x)N_(y) thin film 230 from the horizontal surfaces 222 of the maskfeature 220 and substrate 200 while leaving the spacers 231, or theTiO_(x)N_(y) deposited on, or extending from the sidewalls 221, orvertical surfaces of the mask feature substantially unetched.

As a consequence of this directional etch the TiO_(x)N_(y) thin film 231deposited on or extending from the sidewalls 221 of the mask feature220, or spacers, and the mask feature remain on the substrate. As shownin FIG. 2D and In some embodiments the mask feature 220 can then beremoved with a preferential etch, thereby leaving the free-standingspacers 240 on the substrate 200. In some embodiments the preferentialetch is a wet etch. In preferred embodiments the preferential etch is awet hydrofluoric acid etch. In preferred embodiments of the inventionthe TiO_(x)N_(y) spacers have etch selectivity characteristics such thatthe preferential etch removes substantially all of the mask feature,while leaving the TiO_(x)N_(y) spacers relatively unetched. In preferredembodiments the TiO_(x)N_(y) spacers have etch selectivitycharacteristics substantially similar to those of pure TiO₂.

Once the mask feature has been preferentially etched, the TiO_(x)N_(y)spacers 231 remain on the substrate 200. The TiO_(x)N_(y) which had beendeposited on, or extended from the vertical surfaces of the mask featurenow comprises the spacers 240. Whereas before there had been onefeature, the mask feature, and one space, there are now two features,the TiO_(x)N_(y) spacers, and two spaces. Therefore the spacerdeposition process has doubled the linear density of features on thesubstrate, or doubled the pitch.

Additional Applications

The processes described herein can be used to form TiO_(x)N_(y) filmsfor use in a variety of contexts, for example, in integrated circuitfabrication. A TiO_(x)N_(y) film may be used as, for example, asacrificial film in patterning applications. TiO_(x)N_(y) thin filmsdeposited according to the present disclosure may also be useful as ahard mask layer in integrated circuit fabrication. The inherent surfaceroughness of a conventional titanium oxide hard mask layer may amplifyany latent surface roughness of the underlying substrate. A TiO_(x)N_(y)hard mask deposited according to the present disclosure, however, mayreduce this problem due to the comparatively higher degree of surfaceuniformity and lower crystallinity. In some embodiments the depositedTiO_(x)N_(y) film has a reduced roughness that is a reduced RMSroughness as compared to a roughness of the substrate beforeTiO_(x)N_(y) deposition. In some embodiments the TiO_(x)N_(y) isdeposited on top of a sacrificial film on the substrate surface. In someembodiments the TiO_(x)N_(y) is deposited on top of polymer or resistfilm. In some embodiments the TiO_(x)N_(y) is used as sacrificial layeror film.

Further, TiO_(x)N_(y) thin films deposited according to the presentdisclosure may be used in photocatalytic applications. The nitrogen inthe TiO_(x)N_(y) thin film may serve to modify the band gap energy ofthe film relative to titanium oxide. By controlling the ratio of Ncontaining compounds to O containing compounds in the second reactantthe amount of nitrogen, and thus the band gap energy of the resultantTiO_(x)N_(y) thin film may be tuned as desired.

TiO₂ has the highest refractive index of all the metal oxides and istherefore used in many optical applications. In optical thin films it isoften crucial to have a high degree of smoothness, otherwise surfacefeatures of the film may disrupt performance. In some embodimentsTiO_(x)N_(y) films with various refractive indices (R.I.) may bedeposited. In some embodiments TiO_(x)N_(y) films may be used in opticalapplications, for example in a CIS (CMOS Image Sensor). TiO₂ has alsobeen studied as a gas sensor, as a high-k insulator for MOSFETs andmemory applications, such as DRAMs, as a resistance switching materialin memristors and in implants due to its biocompatibility. In general,smoothness is a desired film characteristic in many of theseapplications. TiO_(x)N_(y) thin films deposited according to the presentdisclosure may exhibit increase smoothness over conventional titaniumoxide films in these applications. In addition, the nitrogen present inthe deposited TiO_(x)N_(y) thin film may modify other film propertieswhich may prove beneficial in certain applications.

EXAMPLE 1

A TiO_(x)N_(y) thin film was deposited according to the presentdisclosure by a PEALD process using TDMAT as the titanium precursor andO₂+N₂ plasma as the second reactant. A susceptor temperature of 190° C.was used. Plasma power was about 400 W and the RF on time was about 0.2seconds. The second reactant was flowed into the chamber with the aid ofan Ar carrier gas. The carrier gas flow rate was about 2 slm. The O₂flow rate was about 0.1 slm while the N2 flow rate was about 1.9 slm.

In addition to the TiO_(x)N_(y) thin film that was deposited, a titaniumoxide reference film was deposited. The titanium oxide thin film wasdeposited by a PEALD processing using TDMAT as the titanium precursorand O₂ plasma as the second reactant. The titanium oxide thin film wasdeposited at the same susceptor temperature, plasma power, and pressureas the TiO_(x)N_(y) thin film. The second reactant was flowed into thechamber with the aid of an Ar carrier gas. The carrier gas flow rate wasabout 2 slm. The O₂ flow rate was about 4 slm.

The WER of the deposited TiO_(x)N_(y) thin film in dHF (1:100) was about68% of the WER of thermal oxide (SiO2). The WER of the titanium oxidethin film in dHF (1:100) was about 57% of the WER of thermal oxide.Therefore, the deposited TiO_(x)N_(y) thin film showed similar WER tothe titanium oxide thin film.

The titanium oxide thin film growth rate per cycle was found to be 0.059nm/cycle, while the TiO_(x)N_(y) thin film growth rate per cycle wasfound to be 0.056 nm/cycle.

Dry Etching

The TiO_(x)N_(y) film was deposited to a thickness of 18.7 nm using 300deposition cycles. The film's growth rate was 0.62 Å/cycle. Thedeposited TiO_(x)N_(y) thin film also showed improved surface roughnessover the titanium oxide reference film as shown in Table 1 below. Theimproved surface roughness can also clearly be seen in FIG. 3A and FIG.3B, which show SEM images taken of the TiO_(x)N_(y) and titanium oxidefilms. With reference to FIG. 3A, the titanium oxide film showed manybumps dispersed over the surface. While, as can be seen in FIG. 3B, veryfew bumps were observed on the surface of the TiO_(x)N_(y) thin film.

TABLE 1 Surface roughness as measured by AFM. TiO TiON R_(a) (nm) 0.150.15 R_(z) (nm) 16 5 R_(q) (nm) 0.2 0.15

The observed step coverage of the deposited TiO_(x)N_(y) thin film wasgreater than 95% for side step coverage and greater than 95% for bottomstep coverage. The side step coverage was observed to range from about91% to about 104%, while the bottom step overage was observed to rangefrom about 96% to about 108%.

The composition of a TiO_(x)N_(y) thin film deposited according to thepresent disclosure was analyzed by XPS. The TiO_(x)N_(y) was found tocomprise 0.5% carbon and 0.3% nitrogen. While these results are notfully understood, the film properties and etch behavior werenevertheless within the specs for the high quality spacer layerapplications.

The terms “film” and “thin film” are used herein for simplicity. “Film”and “thin film” are meant to mean any continuous or non-continuousstructures and material deposited by the methods disclosed herein. Forexample, “film” and “thin film” could include 2D materials, nanorods,nanotubes or nanoparticles or even single partial or full molecularlayers or partial or full atomic layers or clusters of atoms and/ormolecules. “Film” and “thin film” may comprise material or layer withpinholes, but still be at least partially continuous.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. The described features, structures,characteristics and precursors can be combined in any suitable manner.Therefore, it should be clearly understood that the forms of the presentinvention are illustrative only and are not intended to limit the scopeof the present invention. All modifications and changes are intended tofall within the scope of the invention, as defined by the appendedclaims.

What is claimed is:
 1. A process for depositing a titanium oxynitridethin film comprising: contacting a substrate comprising silicon with anorganometallic titanium reactant; subsequently contacting the substratewith a plurality of reactive species generated by plasma from a gas inthe vicinity of the substrate; and repeating the contacting steps untilan amorphous titanium oxynitride thin film comprising from 0.05 at-% to30 at-% of nitrogen has been formed on the substrate, wherein thetitanium oxynitride thin film is deposited at a temperature from 50° C.to 300° C., wherein the plurality of reactive species comprises reactivenitrogen and reactive oxygen species and wherein the ratio of reactivenitrogen species to reactive oxygen species is from 1:1 to 100:1.
 2. Theprocess of claim 1, wherein the gas comprises O₂ gas.
 3. The process ofclaim 1, wherein the gas does not comprise a noble gas.
 4. The processof claim 1, wherein the reactive species comprise nitrogen atoms,nitrogen ions, nitrogen radicals, or nitrogen plasma and oxygen atoms,oxygen radicals, or oxygen plasma.
 5. The process of claim 1, whereinthe gas comprises N₂, NH₃, or N₂H₂.
 6. The process of claim 1, whereinthe gas comprises a noble gas.
 7. The process of claim 6, wherein thegas comprises Ar.
 8. The process of claim 1, wherein the plasma isgenerated by applying RF power of 200 W to 500 W to the gas.
 9. Theprocess of claim 1, further comprising exposing the substrate to a purgegas and/or vacuum to remove excess titanium reactant and reactionbyproducts, if any, after contacting the substrate with the titaniumreactant and prior to contacting the substrate with the reactivespecies.
 10. The process of claim 9, wherein the substrate is movedwithin a single reaction space.
 11. The process of claim 9, wherein thesubstrate is moved from a first reaction space where it is contactedwith the titanium reactant to a second, different reaction space whereit is contacted with the reactive species.
 12. The process of claim 1,further comprising after contacting the substrate with the titaniumreactant moving the substrate such that it is subsequently contactedwith the reactive species.
 13. The process of claim 1, wherein theprocess is used to form spacers for use in a spacer patterning process.14. The process of claim 1, wherein the titanium oxynitride film is asacrificial film in an integrated circuit patterning process.
 15. Theprocess of claim 1, wherein the titanium oxynitride thin film has an RMSsurface roughness of less than about 0.5 nm.
 16. The process of claim 1,wherein the titanium oxynitride thin film has a wet etch rate of 0.01nm/min to 50 nm/min in 1% dHF.
 17. The process of claim 1, wherein thetitanium reactant comprises a titanium alkylamide.
 18. The process ofclaim 1, wherein the titanium reactant comprises an alkylamine ligand.19. The process of claim 1, wherein the titanium reactant comprisesTi(NR^(I)R^(II))₄, wherein R^(I) and R^(II) can be independentlyselected to be alkyl groups.
 20. The process of claim 1, wherein theprocess is a plasma enhanced atomic layer deposition process.
 21. Theprocess of claim 1, wherein the ratio of reactive nitrogen species toreactive oxygen species is from 10:1 to 30:1.